In recent years, a method of introducing a gene of interest into plants and causing the gene to be expressed therein is becoming a generaly used means for conferring a desired trait to plants. However, such expression varies in the plant growth and development stages. For example, the gene is expressed in the young plant period, however, as the growth and development stages proceed, the expression may be attenuated. Therefore, there is a demand for a promoter for expressing an introduced gene in a stable manner regardless of the growth and development stages of plants.
Polypeptide chain elongation factors are involved in polymerization of amino acids by ribosome and are expressed in cells conducting protein synthesis. A chimeric gene in which the promoter region and 5′ terminal region of a polypeptide chain elongation factor 1β (eEF-1β) is fused with a β-glucuronidase (GUS) gene was constructed in Arabidopsis thaliana. This chimeric gene was used to investigate the expression of the gene in transgenic plants (Gene, 170, (1996) 201–206). It was found that the first intron of the gene is required for a high level of expression. This experiment demonstrated that an enhancer-like element may be present in the first intron of the eEF-1β of Arabidopsis thaliana. 
Studies of a rice polypeptide chain elongation factor were reported in FEBS Letters 311 (1992) 46–48, FEBS Letters 338 (1994) 103–106, and Biochemica et Biophysica Acta 1442 (1998) 369–372. FEBS Letters 311 (1992) 46–48 reported cloning and isolation of cDNA encoding the rice polypeptide chain elongation factor 1β′ (EF-1β′). FEBS Letters 338 (1994) 103–106 reported cloning and isolation of cDNA encoding the rice polypeptide chain elongation factor 1β (EF-1β). Biochemica et Biophysica Acta 1442 (1998) 369–372 reported isolation and characterization of EF-1β 2 as a novel gene of a multigene family formed by rice polypeptide chain elongation factors 1β (EF-1β). However, these publications describe that the sequences of the above-described factors were only compared with the sequences of other members of the polypeptide elongation factor family. None of them mentions promoter activity.
Therefore, a promoter of a rice gene, which is permanent and highly active regardless of the growth and development stages of a plant and which is practically usable, will contribute to breeding of useful plants including crops, such as rice and the like, to a great extent.